THERE IS A GENERAL NEED FOR 15N AND 13C LABELED DNA PHOSPHORAMIDITES AND PHOSPHONATES. WE HAVE INVESTIGATED THE SYNTHETIC PROCEDURES WHICH ARE COMMONLY USED FOR THE CONVERSION OF NUCLEOSIDES TO THEIR CORRESPONDING PHOSPHORAMIDITES. THYMINE IS THE ONLY BASE WHICH DOES NOT NEED ANY PROTECTING GROUPS AND THUS, IT IS RELATIVELY STRAIGHTFORWARD TO CONVERT TO ITS PHOSPHORAMIDITE. TREATMENT WITH DIMETHOXYTRITYL CHLORIDE IN PYRIDINE AT 0OC AFFORDS EXCELLENT YIELDS OF THE 5' PROTECTED NUCLEOSIDE. CONVERSION TO THE PHOSPHORAMIDITE IS THEN EFFECTED WITH 2-CYANOETHYL N,N-DIISOPROPYL-CHLOROPHOSPHORAMIDITE USING HUNIGS BASE IN THF AT AMBIENT TEMPERATURE. THE OVERALL YIELD WAS ~75%. ADENOSINE REQUIRES AN ADDITIONAL STEP. THE 5' HYDROXYL IS PROTECTED WITH THE DIMETHOXYTRITYL CHLORIDE, FOLLOWED BY THE PROTECTION OF THE 6-AMINO GROUP WITH BENZOYL CHLORIDE. THE 3' HYDROXYL IS THEN CONVERTED TO THE PHOSPHORAMIDITE IN THE USUAL MANNER. GUANOSINE FIRST REQUIRES THE PROTECTION OF THE 2-AMINO GROUP WITH ISOBUTRYL CHLORIDE AND THE REMAINING GROUPS ARE PROTECTED IN THE USUAL MANNER. CYTOSINE REQUIRES THE PROTECTION OF THE 4-AMINO GROUP WITH BENZOYL CHLORIDE FOLLOWED BY CONVERSION TO ITS PHOSPHORAMIDITE. WE HAVE BECOME FAMILIAR WITH THESE TECHNIQUES TO CONVERT THE MONOMERIC DNA'S TO THEIR PHOSPHORAMIDITES. THESE FUNCTIONALIZED DNA'S ARE THEN USED TO MAKE OLIGOMERIC DNA'S. WE ARE ALSO CURRENTLY EXPLORING THE FEASIBILITY OF USING PHOSPHONATES (R. A. JONES METHOD) TO CONSTRUCT OLIGOMERIC DNA. THE SIR IS CURRENTLY INVOLVED IN THE SYNTHESIS OF THE PHOSPHONATES OF LABELED DNA.